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SANKO GOSEI

Glossary: Sleeve protrusion structure in injection molds

Many of the plastic products we see around us have various functions through assembly (combination of multiple parts).

assembly (combination of multiple parts) to provide a variety of functions.

Boss holes are indispensable for assembly. They are also used for positioning the product, and some products can be made by simply fitting them in.

When injection molding such a boss hole, care must be taken to avoid protrusion of the molded product.

The reason is that the commonly used ejector pin

The boss hole will be held by the ejector pin, making it difficult to remove.

If you try to forcibly remove the molded product, it will be deformed or damaged because it is still hot and soft.

This may cause deformation or breakage of the product.

For product shapes with such boss holes

it is recommended to use a sleeve pin and center pin.

As shown above, it consists of two parts, and the center pin passes through the sleeve pin with a hole in it.

The sleeve pin is fixed to the protruding plate and the center pin is fixed to the fixed plate.

The sleeve pin is fixed to the protruding plate and the center pin is fixed to the fixed plate.

In this way, the sleeve pin protrudes the circumference of the boss during ejection, allowing the boss hole to be pulled out from the pin.

The sleeve pin can be pulled out of the boss hole.

When incorporating the sleeve pin in the mold design

Is the amount of ejection sufficient to pull out the boss hole?

Care must be taken to avoid product sink marks due to temperature rise of the center pin.

In the case of large molded products, depending on the mold structure, sleeve protrusion may not be feasible.

Care must be taken.

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